As many reflex actions are highly expressive,
the subject must here be noticed at some little length.
We shall also see that some of them graduate into, and can hardly
be distinguished from actions which have arisen through habit?
Coughing and sneezing are familiar instances of reflex actions.
With infants the first act of respiration is often a sneeze,
although this requires the co-ordinated movement of numerous muscles.
Respiration is partly voluntary, but mainly reflex, and is performed
in the most natural and best manner without the interference of the will.
A vast number of complex movements are reflex. As good an instance
as can be given is the often-quoted one of a decapitated frog,
which cannot of course feel, and cannot consciously perform, any movement.
Yet if a drop of acid be placed on the lower surface of the thigh
of a frog in this state, it will rub off the drop with the upper
surface of the foot of the same leg. If this foot be cut off,
it cannot thus act. "After some fruitless efforts, therefore, it gives
up trying in that way, seems restless, as though, says Pfluger,
it was seeking some other way, and at last it makes use of
the foot of the other leg and succeeds in rubbing off the acid.
Notably we have here not merely contractions of muscles, but combined
and harmonized contractions in due sequence for a special purpose.
These are actions that have all the appearance of being guided
by intelligence and instigated by will in an animal, the recognized
organ of whose intelligence and will has been removed."[10]

[9] Prof. Huxley remarks (`Elementary Physiology,'
5th edit. p. 305) that reflex actions proper to the spinal cord
are NATURAL; but, by the help of the brain, that is through habit,
an infinity of ARTIFICIAL reflex actions may be acquired.
Virchow admits (`Sammlung wissenschaft. Vortrage,' &c., "Ueber
das Ruckeninark," 1871, ss. 24, 31) that some reflex actions
can hardly be distinguished from instincts; and, of the latter,
it may be added, some cannot be distinguished from inherited habits.

We see the difference between reflex and voluntary movements in
very young children not being able to perform, as I am informed by
Sir Henry Holland, certain acts somewhat analogous to those of sneezing
and coughing, namely, in their not being able to blow their noses (i. e.
to compress the nose and blow violently through the passage),
and in their not being able to clear their throats of phlegm.
They have to learn to perform these acts, yet they are performed
by us, when a little older, almost as easily as reflex actions.
Sneezing and coughing, however, can be controlled by the will only
partially or not at all; whilst the clearing the throat and blowing
the nose are completely under our command.

[10] "Dr. Maudsley, `Body and Mind,' 1870, p. 8.

When we are conscious of the presence of an irritating particle
in our nostrils or windpipe--that is, when the same sensory
nerve-cells are excited, as in the case of sneezing and coughing--
we can voluntarily expel the particle by forcibly driving air
through these passages; but we cannot do this with nearly
the same force, rapidity, and precision, as by a reflex action.
In this latter case the sensory nerve-cells apparently excite
the motor nerve-cells without any waste of power by first
communicating with the cerebral hemispheres--the seat of our
consciousness and volition. In all cases there seems to exist
a profound antagonism between the same movements, as directed
by the will and by a reflex stimulant, in the force with which they
are performed and in the facility with which they are excited.
As Claude Bernard asserts, "L'influence du cerveau tend donc
a entraver les mouvements reflexes, a limiter leur force
et leur etendue."[11]

The conscious wish to perform a reflex action sometimes stops or interrupts
its performance, though the proper sensory nerves may be stimulated.
For instance, many years ago I laid a small wager with a dozen young
men that they would not sneeze if they took snuff, although they all
declared that they invariably did so; accordingly they all took a pinch,
but from wishing much to succeed, not one sneezed, though their
eyes watered, and all, without exception, had to pay me the wager.
Sir H.